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Gatto F, Benemei S, Piluso G, Bello L. The complex landscape of DMD mutations: moving towards personalized medicine. Front Genet 2024; 15:1360224. [PMID: 38596212 PMCID: PMC11002111 DOI: 10.3389/fgene.2024.1360224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 02/26/2024] [Indexed: 04/11/2024] Open
Abstract
Duchenne muscular dystrophy (DMD) is a severe genetic disorder characterized by progressive muscle degeneration, with respiratory and cardiac complications, caused by mutations in the DMD gene, encoding the protein dystrophin. Various DMD mutations result in different phenotypes and disease severity. Understanding genotype/phenotype correlations is essential to optimize clinical care, as mutation-specific therapies and innovative therapeutic approaches are becoming available. Disease modifier genes, trans-active variants influencing disease severity and phenotypic expressivity, may modulate the response to therapy, and become new therapeutic targets. Uncovering more disease modifier genes via extensive genomic mapping studies offers the potential to fine-tune prognostic assessments for individuals with DMD. This review provides insights into genotype/phenotype correlations and the influence of modifier genes in DMD.
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Affiliation(s)
| | | | - Giulio Piluso
- Medical Genetics and Cardiomyology, Department of Precision Medicine, University of Campania “Luigi Vanvitelli”, Napoli, Italy
| | - Luca Bello
- Department of Neurosciences DNS, University of Padova, Padova, Italy
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Gushchina LV, Bradley AJ, Vetter TA, Lay JW, Rohan NL, Frair EC, Wein N, Flanigan KM. Persistence of exon 2 skipping and dystrophin expression at 18 months after U7snRNA-mediated therapy in the Dup2 mouse model. Mol Ther Methods Clin Dev 2023; 31:101144. [PMID: 38027058 PMCID: PMC10679948 DOI: 10.1016/j.omtm.2023.101144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 10/24/2023] [Indexed: 12/01/2023]
Abstract
Duchenne muscular dystrophy (DMD) is a progressive X-linked disease caused by mutations in the DMD gene that prevent the expression of a functional dystrophin protein. Exon duplications represent 6%-11% of mutations, and duplications of exon 2 (Dup2) are the most common (∼11%) of duplication mutations. An exon-skipping strategy for Dup2 mutations presents a large therapeutic window. Skipping one exon copy results in full-length dystrophin expression, whereas skipping of both copies (Del2) activates an internal ribosomal entry site (IRES) in exon 5, inducing the expression of a highly functional truncated dystrophin isoform. We have previously confirmed the therapeutic efficacy of AAV9.U7snRNA-mediated skipping in the Dup2 mouse model and showed the absence of off-target splicing effects and lack of toxicity in mice and nonhuman primates. Here, we report long-term dystrophin expression data following the treatment of 3-month-old Dup2 mice with the scAAV9.U7.ACCA vector. Significant exon 2 skipping and robust dystrophin expression in the muscles and hearts of treated mice persist at 18 months after treatment, along with the partial rescue of muscle function. These data extend our previous findings and show that scAAV9.U7.ACCA provides long-term protection by restoring the disrupted dystrophin reading frame in the context of exon 2 duplications.
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Affiliation(s)
- Liubov V. Gushchina
- The Center for Gene Therapy, Nationwide Children’s Hospital and The Ohio State University, Columbus, OH, USA
- Department of Pediatrics, The Ohio State University, Columbus, OH, USA
| | - Adrienne J. Bradley
- The Center for Gene Therapy, Nationwide Children’s Hospital and The Ohio State University, Columbus, OH, USA
| | - Tatyana A. Vetter
- The Center for Gene Therapy, Nationwide Children’s Hospital and The Ohio State University, Columbus, OH, USA
- Department of Pediatrics, The Ohio State University, Columbus, OH, USA
| | - Jacob W. Lay
- The Center for Gene Therapy, Nationwide Children’s Hospital and The Ohio State University, Columbus, OH, USA
| | - Natalie L. Rohan
- The Center for Gene Therapy, Nationwide Children’s Hospital and The Ohio State University, Columbus, OH, USA
| | - Emma C. Frair
- The Center for Gene Therapy, Nationwide Children’s Hospital and The Ohio State University, Columbus, OH, USA
| | - Nicolas Wein
- The Center for Gene Therapy, Nationwide Children’s Hospital and The Ohio State University, Columbus, OH, USA
- Department of Pediatrics, The Ohio State University, Columbus, OH, USA
| | - Kevin M. Flanigan
- The Center for Gene Therapy, Nationwide Children’s Hospital and The Ohio State University, Columbus, OH, USA
- Department of Pediatrics, The Ohio State University, Columbus, OH, USA
- Department of Neurology, The Ohio State University, Columbus, OH, USA
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Stephenson AA, Nicolau S, Vetter TA, Dufresne GP, Frair EC, Sarff JE, Wheeler GL, Kelly BJ, White P, Flanigan KM. CRISPR-Cas9 homology-independent targeted integration of exons 1-19 restores full-length dystrophin in mice. Mol Ther Methods Clin Dev 2023; 30:486-499. [PMID: 37706184 PMCID: PMC10495553 DOI: 10.1016/j.omtm.2023.08.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 08/15/2023] [Indexed: 09/15/2023]
Abstract
Duchenne muscular dystrophy is an X-linked disorder typically caused by out-of-frame mutations in the DMD gene. Most of these are deletions of one or more exons, which can theoretically be corrected through CRISPR-Cas9-mediated knockin. Homology-independent targeted integration is a mechanism for achieving such a knockin without reliance on homology-directed repair pathways, which are inactive in muscle. We designed a system based on insertion into intron 19 of a DNA fragment containing a pre-spliced mega-exon encoding DMD exons 1-19, along with the MHCK7 promoter, and delivered it via a pair of AAV9 vectors in mice carrying a Dmd exon 2 duplication. Maximal efficiency was achieved using a Cas9:donor adeno-associated virus (AAV) ratio of 1:5, with Cas9 under the control of the SPc5-12 promoter. This approach achieved editing of 1.4% of genomes in the heart, leading to 30% correction at the transcript level and restoration of 11% of normal dystrophin levels. Treatment efficacy was lower in skeletal muscles. Sequencing additionally revealed integration of fragmentary and recombined AAV genomes at the target site. These data provide proof of concept for a gene editing system that could restore full-length dystrophin in individuals carrying mutations upstream of intron 19, accounting for approximately 25% of Duchenne muscular dystrophy patients.
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Affiliation(s)
- Anthony A. Stephenson
- Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Stefan Nicolau
- Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Tatyana A. Vetter
- Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
- Department of Pediatrics, The Ohio State University, Columbus, OH 43210, USA
| | - Gabrielle P. Dufresne
- Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Emma C. Frair
- Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Jessica E. Sarff
- Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Gregory L. Wheeler
- The Institute for Genomic Medicine, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Benjamin J. Kelly
- The Institute for Genomic Medicine, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Peter White
- Department of Pediatrics, The Ohio State University, Columbus, OH 43210, USA
- The Institute for Genomic Medicine, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Kevin M. Flanigan
- Center for Gene Therapy, The Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205, USA
- Department of Pediatrics, The Ohio State University, Columbus, OH 43210, USA
- Department of Neurology, The Ohio State University, Columbus, OH 43210, USA
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Bello L, Hoffman EP, Pegoraro E. Is it time for genetic modifiers to predict prognosis in Duchenne muscular dystrophy? Nat Rev Neurol 2023; 19:410-423. [PMID: 37308617 DOI: 10.1038/s41582-023-00823-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/11/2023] [Indexed: 06/14/2023]
Abstract
Patients with Duchenne muscular dystrophy (DMD) show clinically relevant phenotypic variability, despite sharing the same primary biochemical defect (dystrophin deficiency). Factors contributing to this clinical variability include allelic heterogeneity (specific DMD mutations), genetic modifiers (trans-acting genetic polymorphisms) and variations in clinical care. Recently, a series of genetic modifiers have been identified, mostly involving genes and/or proteins that regulate inflammation and fibrosis - processes increasingly recognized as being causally linked with physical disability. This article reviews genetic modifier studies in DMD to date and discusses the effect of genetic modifiers on predicting disease trajectories (prognosis), clinical trial design and interpretation (inclusion of genotype-stratified subgroup analyses) and therapeutic approaches. The genetic modifiers identified to date underscore the importance of progressive fibrosis, downstream of dystrophin deficiency, in driving the disease process. As such, genetic modifiers have shown the importance of therapies aimed at slowing this fibrotic process and might point to key drug targets.
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Affiliation(s)
- Luca Bello
- Department of Neurosciences (DNS), University of Padova, Padova, Italy
| | - Eric P Hoffman
- School of Pharmacy and Pharmaceutical Sciences, Binghamton University (State University of New York), Binghamton, NY, USA
| | - Elena Pegoraro
- Department of Neurosciences (DNS), University of Padova, Padova, Italy.
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Findlay AR, Weihl CC. Genetic-Based Treatment Strategies for Muscular Dystrophy and Congenital Myopathies. Continuum (Minneap Minn) 2022; 28:1800-1816. [PMID: 36537981 PMCID: PMC10496150 DOI: 10.1212/con.0000000000001203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
PURPOSE OF REVIEW This article discusses the foundational concepts of genetic treatment strategies employed in neuromuscular medicine, as well as the importance of genetic testing as a requirement for applying gene-based therapy. RECENT FINDINGS Gene therapies have become a reality for several neuromuscular disorders. Exon-skipping and (in Europe) ribosomal read-through approaches are currently available to a subset of patients with Duchenne muscular dystrophy. Microdystrophin gene replacement has shown promise and is nearing the final stages of clinical trials. Numerous gene-based therapies for other muscular dystrophies and congenital myopathies are progressing toward approval as well. SUMMARY Muscular dystrophies and congenital myopathies are a heterogenous group of hereditary muscle disorders. Confirming a diagnosis with genetic testing is not only critical for guiding management, but also an actual prerequisite for current and future gene therapies. Recessive loss-of-function or dominant haploinsufficiency disorders may be treated with gene replacement strategies, whereas dominant negative and toxic gain-of-function disorders are best addressed with a variety of knockdown approaches. It is important to recognize that many therapeutics are mutation specific and will only benefit a subset of individuals with a specific disease.
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Wein N, Vetter TA, Vulin A, Simmons TR, Frair EC, Bradley AJ, Gushchina LV, Almeida CF, Huang N, Lesman D, Rajakumar D, Weiss RB, Flanigan KM. Systemic delivery of an AAV9 exon-skipping vector significantly improves or prevents features of Duchenne muscular dystrophy in the Dup2 mouse. Mol Ther Methods Clin Dev 2022; 26:279-293. [PMID: 35949298 PMCID: PMC9356240 DOI: 10.1016/j.omtm.2022.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Accepted: 07/08/2022] [Indexed: 11/17/2022]
Abstract
Duchenne muscular dystrophy (DMD) is typically caused by mutations that disrupt the DMD reading frame, but nonsense mutations in the 5′ part of the gene induce utilization of an internal ribosomal entry site (IRES) in exon 5, driving expression of a highly functional N-truncated dystrophin. We have developed an AAV9 vector expressing U7 small nuclear RNAs targeting DMD exon 2 and have tested it in a mouse containing a duplication of exon 2, in which skipping of both exon 2 copies induces IRES-driven expression, and skipping of one copy leads to wild-type dystrophin expression. One-time intravascular injection either at postnatal days 0–1 or at 2 months results in efficient exon skipping and dystrophin expression, and significant protection from functional and pathologic deficits. Immunofluorescence quantification showed 33%–53% average dystrophin intensity and 55%–79% average dystrophin-positive fibers in mice treated in adulthood, with partial amelioration of DMD pathology and correction of DMD-associated alterations in gene expression. In mice treated neonatally, dystrophin immunofluorescence reached 49%–85% of normal intensity and 76%–99% dystrophin-positive fibers, with near-complete correction of dystrophic pathology, and these beneficial effects persisted for at least 6 months. Our results demonstrate the robustness, durability, and safety of exon 2 skipping using scAAV9.U7snRNA.ACCA, supporting its clinical use.
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Affiliation(s)
- Nicolas Wein
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA.,Department of Pediatrics, The Ohio State University, Columbus, OH, USA
| | - Tatyana A Vetter
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Adeline Vulin
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Tabatha R Simmons
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Emma C Frair
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Adrienne J Bradley
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Liubov V Gushchina
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Camila F Almeida
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Nianyuan Huang
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Daniel Lesman
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Dhanarajan Rajakumar
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA
| | - Robert B Weiss
- Department of Human Genetics, The University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Kevin M Flanigan
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA.,Department of Pediatrics, The Ohio State University, Columbus, OH, USA.,Department of Neurology, The Ohio State University, Columbus, OH, USA
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